In the construction of some types of hollow fiber membrane devices such as blood dialysis cartridges, the hollow fibers are terminated in tube sheets of cast plastic. As part of the manufacturing process, the tube sheets are cut to expose the inner hollow fiber passages to fluid headers. Such cutting and machining produce sharp edges at the surfaces where the hollow fibers emerge from the tube sheet intersections. Depending upon the cutting and machining method, the cut surface may contain rough edges, burrs, microfibers and other micro-size surface structures and sharp edges. This kind of micro-fuzzy surface has the same behavior as a microfiber filter which captures micro-particles from a fluid suspension at fixed sites having microradii.
In the operation of hollow fiber membrane devices with complex fluids having metastable suspensions of various particles such as animal blood, the precipitation of fluid components by the sharp edge mechanism produces particle deposits on the ends of the hollow fibers, and forms thrombi and emboli some of which become detached and block the hollow fibers internally or at fiber entrance points.
Specifically, in the operation of hollow fiber dialyzers as an artificial kidney for the treatment of blood, the sharp edge precipitation mechanism results in partial or complete blockage of the blood flow through the hollow fibers, depending upon the length of use and individual blood characteristics. The blocked hollow fibers decrease the membrane dialysis transfer area and thus degrade the performance of the artificial kidney.